thank you for that precise explanation.
objdump is now less cryptic to me...
- ben
Glynn Clements a écrit :
ben wrote:
i don't know if it is a compiler feature (storage behavior into the DATA
segment), or a linux kernel feature, or if it is specified in ANSI, but
the second way leads to pointing to a _constant_ string. If someone can
enlighten...
ANSI C says that string literals "may" be read-only. On platforms with
memory protection they usually are read-only.
On Linux, string literals are stored in the "rodata" segment, which is
read-only, and thus can be shared between all processes which are
using a given executable or shared library.
You can list the segments which make up an executable or shared
library using "objdump -h"
[snipped]
The main ones are text, rodata, data, and bss.
The text segment holds code, and is read-only and executable (CODE
flag).
The others hold static data: global variables, "static" local
variables, string literals, and intialisers for automatic
(non-"static" local) arrays.
Read-only data (literals, initialisers, "const" variables) goes into
the rodata segment, which is read-only.
Mutable variables with explicit initialisers go into the data segment.
Mutable variables without initialisers (i.e. implicitly initialised to
zero) go into the bss segment. As the entire bss segment is initially
zero, it doesn't need to be stored in the file (this is indicated by
the lack of the CONTENTS, LOAD, and CODE/DATA flags).
The other segments tend to be architecture-specific.
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